Various wireless communication technologies systems have been developed with rapid development of information communication technologies. WLAN technology from among the wireless communication technologies allows wireless Internet access at home or in enterprises or at a specific service zone using mobile terminals, such as a Personal Digital Assistant (PDA), a laptop computer, a Portable. Multimedia Player (PMP), etc. on the basis of Radio. Frequency (RF) technology.
In order to obviate limited communication speed pointed out as a drawback in the WLAN, the recent technical standard has proposed an evolved system capable of increasing the speed and reliability of a network while simultaneously extending a coverage region of a wireless network. For example, IEEE 802.11n enables a data processing speed to support high throughput (HT) of maximum 540 Mbps. In addition, Multiple. Input and Multiple Output (MIMO) technology has recently been applied to both a transmitter and a receiver so as to minimize transmission errors as well as to optimize a data transfer rate.
Machine to Machine (M2M) communication technology has been discussed as next generation communication technology. A technical standard for supporting M2M communication in IEEE 802.11 WLAN system has been developed as IEEE 802.11ah. M2M communication may consider a scenario capable of sometimes communicating a small amount of data at low speed in an environment where a large number of devices exist.
In the wireless LAN system, communication is performed in a medium shared between all the devices. If the number of devices is increased in the same manner as M2M communication, it is required to more efficiently improve a channel access mechanism to reduce unnecessary power consumption and occurrence of interference.